Pin tumbler lock is one of the most common lock in the market and conventionally includes a housing, a plug, top pins and bottom pins. The top pins are placed in an accommodation space of the housing and the bottom pins corresponding to the top pins are placed in linear grooves of the plug. The top pins are pushed by springs to push the bottom pins and cross a shear line between the plug and the housing because of the bottom pins having different lengths such that can block the turning of the plug for locking. When a key is inserted into a key way of the plug, the bottom pins and the top pins are pushed upward. And if the inserted key is the correct key, it can rotate the plug to unlock because the boundary between the top and bottom pins is pushed to align along the shear line.
Based on the stability and security, the top and bottom pins of the conventional pin tumbler lock are confined in the accommodation space of the housing and the linear grooves of the plug, respectively, and it is difficult to take out the pins from the lock. Key replacement of the conventional lock is not easy because the shapes of the key cuts are determined by the lengths of the bottom pins that cannot be removed from the lock. As a result, the whole lock has to be changed when intending to replace the key.